Friction stir bonding method

ABSTRACT

The object of the present invention is to provide a friction stir bonding method that could provide good bonding at the butted region with the concave portion and convex portion fitted together.  
     End portions of materials  10, 20  are abutted against each other. A trapezoidal convex portion  22  of the material  20  is inserted into a trapezoidal concave portion  12  of the material  10.  A friction stir bonding is performed by inserting a rotary tool  50  from the side of convex portions  13, 23.  A small-diameter portion  51   b  of the rotary tool  50  is tapered, and is provided with a screw  51   b.  A large-diameter portion  53  is of a member different from an axis portion of the rotary tool  50,  and is connected by a pin  59.  The screw of the screw portion  51   b  could be formed to the vicinity of a concave  53   g  of an end surface of the large-diameter portion  53,  so that stirring near the end surface could be performed sufficiently. Therefore, good friction stir bonding could be achieved.

FIELD OF THE INVENTION

[0001] The present invention relates to a friction stir bonding method.

DESCRIPTION OF THE RELATED ART

[0002] A friction stir bonding method is a technique using a round shaft (called a rotary tool) being inserted into the bonding region of members and moving the rotating rotary tool along the junction line, thereby heating, mobilizing and plasticising the bonding region, and realizing a solid-phase bonding of the members. The rotary tool comprises a large-diameter portion and the small-diameter portion at the leading end thereof. The bonding is performed by inserting the small-diameter portion into the member to be bonded, and placing the end surface of the large-diameter portion in contact with the aforementioned member. A screw is formed to the small-diameter portion. The end surface of the large-diameter portion on the screw portion side is concaved. Moreover, a friction stir bonding may be performed by positioning a member to be bonded between two large-diameter portions of the rotary tool. This technique is disclosed in Japanese Patent No. 2,712,838 (U.S. Pat. No. 5,460,317), and Japanese Patent National Publication of PCT Application No. 9-508073 (EP 0752926B1).

SUMMARY OF THE INVENTION

[0003] The case of friction stir bonding the butted region between two extruded materials 10, 20 made of aluminum alloy will be considered, as is illustrated in FIG. 4. A trapezoidal concave portion 12 is provided at the end surface of the face plate 11 of the material 10, and a trapezoidal convex portion 22 is provided at the end surface of the face plate 21 of the material 20. The convex portion 22 is inserted into the concave portion 12. The concave portion 12 and the convex portion 22 take the trapezoid shape to simplify insertion. Also, the end portions of the materials 10, 20 are provided with second convex portions 13, 23 projecting upwardly. In the case where the materials 10, 20 are a car body of a railway car, the length of the materials 10, 20 is approximately 20 m. Therefore, the materials 10, 20 at the butted region tend to constitute a substantially different plane. In order to prevent such situation, the end surfaces of the butted region are provided with the concave portion 12 and the convex portion 22, and are fitted against each other.

[0004] In such state, the friction stir bonding is performed by inserting a small-diameter portion 51 of a rotary tool 50 from above, and inserting the end surface of a large-diameter portion 53 (end surface on the small-diameter portion 51 side) into the convex portions 13, 23, and rotating and moving the rotary tool 50 along the butted region, as is illustrated in FIG. 9. Reference number 100 indicates a bed for fixing the materials 10, 20.

[0005] The rotary tool 50 used for bonding is shown in FIG. 10. The rotary tool 50 has a small-diameter portion 51 to the leading end of the large-diameter portion 53. The small-diameter portion 51 takes the tapered shape having larger diameter towards the leading end. This is to stir the butted region of the concave portion 12 and the convex portion 22 sufficiently. The tapered surface of the small-diameter portion 51 is provided with a male screw. The end surface 53 h of the large-diameter portion 53 is concaved towards the large-diameter portion 53.

[0006] The small-diameter portion 51 in the vicinity of the large-diameter 53 (the small-diameter portion 51 on the base end side) is not provided with the screw. This is because it is difficult to provide the screw to the small-diameter portion 51 on the base end side. This is because the small-diameter portion 51 is tapered.

[0007] In FIG. 9, the region of the small-diameter portion 51 without the screw is placed at the position of the upper slopes (called sides) 12 b, 22 b of the trapezoidal concave portion 12 and the trapezoidal convex portion 22. Therefore, the stirring in this region tends to be insufficient. When stirring is insufficient, it is considered to have an influence on the strength. In the case where the material to be bonded is aluminum alloy, the surface of the materials 10, 20 tends to be oxidized. When stirring is insufficient, it is considered that such metal oxide has bad influence on the strength.

[0008] The object of the present invention is to provide a friction stir bonding method that could provide good bonding at the butted region with the concave portion and convex portion fitted together.

[0009] The present invention is characterized in performing friction stir bonding by positioning a screw to the fitted region of the concave portion and the convex portion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a longitudinal cross-sectional view during bonding according to one embodiment of the present invention;

[0011]FIG. 2 is a side view of a rotary tool in FIG. 1;

[0012]FIG. 3 is a disassembled longitudinal cross-sectional view of a rotary tool in FIG. 2;

[0013]FIG. 4 is a longitudinal cross-sectional view of a pair of extruded materials in FIG. 1;

[0014]FIG. 5 is a perspective view of a car body of a railway car;

[0015]FIG. 6 is a longitudinal cross-sectional view during bonding according to another embodiment of the present invention;

[0016]FIG. 7 is a disassembled longitudinal cross-sectional view of a rotary tool in FIG. 6;

[0017]FIG. 8 is a longitudinal cross-sectional view during assembling of the rotary tool in FIG. 6;

[0018]FIG. 9 is a longitudinal cross-sectional view during bonding according to conventional technique; and

[0019]FIG. 10 is a longitudinal cross-sectional view of a conventional rotary tool.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0020] A preferred embodiment of the present invention will now be explained with reference to FIG. 1 through FIG. 5. A car body 500 of a railway car is comprised of a side structure 501 constituting the side surface, a roof structure 502 constituting the roof, an underframe 503 constituting the floor, and an end structure 504 constituting the end portion in the longitudinal direction. The side structure 501, the roof structure 502, and the underframe 503 are formed by bonding plural extruded materials 10, 20, respectively. The longitudinal direction (extruded direction) of the extruded materials 10, 20 is positioned toward the longitudinal direction of the car body 500. The extruded materials 10, 20 are made of aluminum alloy. There exists a plurality of ribs at the inner side of the car body, that is, at the convex portions 13, 23 side of the face plates 11, 21, that are not shown in the figures. The structure of the butted region of the materials 10, 20 are as mentioned earlier.

[0021] The members of a rotary tool 50 are comprised of a round shaft 50 b including the small-diameter portion 51, and a member 53 b for the large-diameter portion 53. To the end portion of the small-diameter portion of the round shaft 50 b, from the leading end side, there exists a screw portion 51 b including a screw on a tapered small-diameter portion, and an axis portion 51 c for fixing the member 53 b for the large-diameter portion. The leading end of the screw portion 51 b has a larger diameter. A pin hole 51 f for fixing the member 53 b for the large-diameter portion is provided on the axis portion 51 c.

[0022] The member 53 b corresponds to the large-diameter portion 53, and is circular at the outer shape thereof. The member 53 b has a hole 53 c to be fitted to the axis portion 51 c. The difference between the diameter of the axis portion 51 c and the diameter of the hole 53 c is small. The member 53 b includes a pin hole 53 f. The member 53 b is inserted into the axis portion 51 c, and is fixed with a knock pin 58.

[0023] The end surface of the member 53 b facing the screw portion 51 b is provided with a concave 53 g. The depth of the concave 53 g is deeper towards the screw portion 51 b, and is shallower towards the outer peripheral portion. The concave 53 g holds the metal to be bonded, and restricts the outflow of the metal from the end surface of the large-diameter portion 53. This is similar to the concave 53 h.

[0024] The length L1 of the axis portion 51 c is shorter than the length L3 of the member 53 b. The length L2 of the screw portion 51 b is longer than the length of the conventional screw portion 51 by the calculation of the difference (L3−L1). The length of the screw is elongated relative to the increase of the length L2 of the screw portion 51 b. The end portion 53 d at the inner diameter side of the concave 53 g of the member 53 b is positioned at the end surface 51 d of the axis portion 51 c. Therefore, when the member 53 b is mounted to the axis portion 51 c, the screw is positioned inside the concave 53 g. Or, the screw is positioned in the vicinity of the end portion in the axial direction of the outer peripheral portion of the member 53 b.

[0025] The diameter D of the large-diameter portion 53 is smaller than the sum width W of the width W1 and W2 of the two convex portions 13, 23, respectively. The metal at the convex portions 13, 23 becomes the source for filling the gap at the butted region between the two materials 10, 20. Also, during friction stir bonding, the lowermost end of the large-diameter portion 53 is positioned inside the convex portions 13, 23. By saying that the large-diameter portion 53 is positioned inside the convex portions 13, 23, it means that the lowermost end of the large-diameter portion 53 is positioned above the upper surface of the face plates 11, 21 excluding the convex portions 13, 23. As is well-known in the art, the axis of rotation of the rotary tool 50 is inclined relative to the direction of movement. The axis of rotation is inclined so that the axial center on the side of the small-diameter portion 51 is positioned toward the side of the direction of movement than the axial center on the side of the large-diameter portion 53. The lowermost end at the rear end of the lower end of the large diameter portion 53 is positioned inside the convex portions 13, 23.

[0026] The friction stir bonding is performed by placing the axial center of the rotary tool 50 at approximately the center of the concave portion 12 in the depth direction. Therefore, the width W1 of the convex portion 13 is larger than the width W2 of the convex portion 23. A driving device for rotating and moving the tool is placed at the upper end of the round shaft 50 b.

[0027] With such structure, the screw of screw portion 51 b is formed to the vicinity of the end surface of the large-diameter portion (end surface on the side of the screw portion 51 b, the base end side of the screw portion 51 b). Therefore, the upper slopes (called sides) 12 b, 22 b of the butted trapezoid portion are stirred with the screw, so as to be stirred in the axial direction. Therefore, the problem concerning strength arising from the metal oxide is inhibited.

[0028] In the above-mentioned embodiment, the screw portion 51 b is tapered. However, even in the case of the non-tapered (called a linear) screw portion 51 b, the similar problem occurs because it is difficult to form the screw to the vicinity of the end surface of the large-diameter portion 53. Therefore, the large-diameter portion should be formed as an independent member, even in the case of linear screw portion, as is illustrated in FIG. 7.

[0029] In the above-mentioned embodiment, the large-diameter portion 53 b is connected with the pin 58. However, it may be fixed by shrinking. Moreover, the large-diameter portion 53 b may be fixed by forming a screw to the axis portion 51 c, and screwing thereto. In this case, the screw should be a reverse screw opposite to the direction of rotation.

[0030] Furthermore, in the case of performing bonding using a conventional rotary tool 50 having no screw near the end surface of the large-diameter portion 53, the upper slopes 12 b, 22 b of the trapezoid of the concave portion 12 and convex portion 22 are adjusted to the position of the screw of the small-diameter portion 51.

[0031] Also, the upper slopes 12 b, 22 b of the trapezoid of the concave portion 12 and convex portion 22 are provided inside the convex portions 13, 23, and bonding is performed using a conventional rotary tool 50 having no screw near the end surface of the large-diameter portion 53. Subsequently, in order to eliminate the incompletely stirred portion therefrom, the convex portions 13, 23 are cut out. By doing so, insufficient stirred portion does not exist in the remaining portion, so that there exists no problem concerning strength.

[0032] Another embodiment shown in FIG. 6 through FIG. 9 will now be explained. The embodiment concerns providing large-diameter portions 63, 64 at either end of the screw portion 61 b of the small-diameter portion 61, and performing friction bonding by interposing the butted region between the two large-diameter portions 63, 64.

[0033] A rotary tool 60 is comprised of a round shaft 60 b including a small-diameter portion 61, and members 63 b, 64 b for large-diameter portions 63, 64. The members 63 b, 64 b are fixed to the axis portions 61 c, 61 d of the round shaft 60 b with a knock pin. The small-diameter portion 61 is provided with, from the leading end side, the axis portion 61 d for fixing the member 64 b, a screw portion 61 b, and the axis portion 61 c for fixing the member 63 b. The screw portion 61 b is linear. The diameter of the axis portion 61 c is identical to that of the screw portion 61 b. The diameter of the axis portion 61 d is smaller than that of the screw portion 61 b. The length of ordinary screw of the screw portion 61 b is longer than the length L. The position of the screw portion 61 b depends on the shape of the concaves 63 h, 64 h. There are provided pin holes 61 f, 61 g to the axis portions 61 c, 61 d.

[0034] The members 63 b, 64 b include holes 63 c, 64 c having the diameter fitting with the axis portions 61 c, 61 d. The difference between the diameter of the axis portions 61 c, 61 d and that of the holes 63 c, 64 c is small. There are provided pin holes 63 d, 64 d to the members 63 b, 64 b. The members 63 b, 64 b are provided with concaves 63 h, 64 h having the similar object with the aforementioned concaves 53 h, 53 g at the end surface facing the screw portion 61 b. The end portions 63 j, 64 j at the inner diameter side of the concaves 63 h, 64 h are in a concaved position relative to axial ends 63 k, 64 k at the outer peripheral side of the members 63 b, 64 b. By doing so, the end portion of the screw on the side of the large-diameter portion 63 is positioned inside the concave 63 h of the large-diameter portion 63, as is illustrated in the assembly view of FIG. 8. The end portion of the screw on the side of the large-diameter portion 64 is positioned inside the concave 64 h of the large-diameter portion 64.

[0035] Upon bonding, the lower end of the large-diameter portion 63 is inserted into the convex portions 13, 23, as is the case in the aforementioned embodiment. The rotary tool 60 is inclined, as is the case in the aforementioned embodiment. The front end of the large-diameter portion 64 of the leading end on the screw portion 61 b side is inserted into the lower portion of the face plates 11, 21. When performing friction stir bonding, the metal is slightly raised against the lower surface of the face plates 11, 21 at the rearward of the large-diameter portion 64. When using the lower surface of the face plates 11, 21 as the outer surface of the car body, the raised metal mentioned above is cut out to obtain a flat surface.

[0036] By doing so, the upper slopes 12 b, 22 b of the trapezoid portion could sufficiently be stirred. Also, the lower side of the face plates 11, 21 could sufficiently be stirred. Therefore, the whole range of the butted region of the face plates 11, 21 could sufficiently be stirred.

[0037] In the above-mentioned embodiment, the end portions 63 j, 64 j of the concaves 63 h, 64 h on the inner diameter side is formed inwardly relative to the end portions 63 k, 64 k of the large portions 63, 64. However, they may be formed at the identical position. Furthermore, the concaves 63 h, 64 h may be formed nearer towards the end portion of the screw. Also, a screw may be formed to the axis portion 61 c continuing from the screw portion 61 b, in order to fix the large-diameter portion 63 thereon. This could also be applied to a rotary tool having no large-diameter portion at the leading end.

[0038] The technical scope of the present invention is not limited to the terms used in the claims or in the summary of the present invention, but is extended to the range in which a person skilled in the art could easily substitute based on the present disclosure.

[0039] The present invention enables good bonding, in a case of friction bonding the fitted region with the trapezoidal concave portion and convex portion. 

We claim:
 1. A friction stir bonding method, the method comprising the steps of; butting an end portion of a first member against an end portion of a second member; inserting a convex portion projecting in said butted direction from said end portion of said first member into a concave portion formed to said end portion of said second member; and friction stir bonding using a rotary tool made of a large-diameter portion and a small-diameter portion being equipped with a screw, by inserting said small-diameter portion into said butted region, in the state where said screw is positioned at sides of said concave portion and said convex portion on said large-diameter portion side.
 2. A friction stir bonding method according to claim 1, wherein: said concave portion takes a trapezoid-shape and said convex portion takes a trapezoid-shape; and said sides of said concave portion and said convex portion are slopes of said trapezoid-shape of said concave portion and said convex portion, and said friction stir bonding is performed in the state where said screw is positioned at said slope.
 3. A friction stir bonding method, the method comprising the steps of; butting an end portion of a first member against an end portion of a second member; inserting a convex portion projecting in said butted direction from said end portion of said first member into a concave portion formed to said end portion of said second member; and friction stir bonding using a rotary tool provided with a large-diameter portion of a member different from that of a small-diameter portion on an axis portion on one end of said small-diameter portion being equipped with a screw, by inserting said small-diameter portion into said butted region, in the state where said screw is positioned at sides of said concave portion and said convex portion on said large-diameter portion side.
 4. A friction stir bonding method according to claim 3, wherein: said concave portion takes the trapezoid-shape and said convex portion takes the trapezoid-shape; and said sides of said concave portion and said convex portion are slopes of said trapezoid-shape of said concave portion and said convex portion, and said friction stir bonding is performed in the state where said screw is positioned at said slope.
 5. A friction stir bonding method according to claim 3, wherein: said small-diameter portion is tapered having larger diameter on one end side than said one end side; and an end surface of said large-diameter portion on said small-diameter portion side is concaved.
 6. A friction stir bonding method, the method comprising the steps of; butting an end portion of a first member against an end portion of a second member; using a rotary tool, with a large-diameter portion of a member different from that of a small-diameter portion provided on an axis portion on one end of said small-diameter portion being equipped with a screw, with the surface of said large-diameter portion facing said small-diameter portion being concaved, and with an end portion of said screw being positioned inside said concave; and friction stir bonding by inserting said small-diameter portion into said butted region.
 7. A friction stir bonding method, the method comprising the steps of; butting an end portion of a first member against an end portion of a second member; equipping a small-diameter portion being equipped with a screw to the leading end of a large-diameter portion, and providing a second large-diameter portion of a member different from that of said small-diameter portion to an axis portion at the leading end of said small-diameter portion; using a rotary tool including end surfaces of said large-diameter portion and said second large-diameter potion facing said small-diameter portion being concaved; and friction stir bonding while interposing said butted region between said large-diameter portion and said second large-diameter portion.
 8. A friction stir bonding method according to claim 7, wherein: said end portion of said first member includes a trapezoid-shaped convex portion projecting in said butting direction, and said end portion of said second member includes a trapezoid-shaped concave portion inserted with said convex portion; and friction stir bonding is performed in the state where said screw is positioned at sides of said concave portion and said convex portion on said large-diameter portion side.
 9. A friction stir bonding method according to claim 7, wherein an end portion of said screw on said second large-diameter portion side exists inside said concave of said second large-diameter portion.
 10. A friction stir bonding method according to claim 7, wherein said large-diameter portion and said small-diameter portion are of a different member, and an end portion of said screw on said large-diameter portion side exists inside said concave of said large-diameter portion.
 11. A friction stir bonding method, the method comprising the steps of: butting an end portion of a first member including a first convex portion projecting in the thickness direction against an end portion of a second member including a first convex portion projecting in the thickness direction; inserting a second convex portion projecting in said butting direction provided on said end portion including said first convex portion of said first member into a convex portion provided on said end portion including said first convex portion of said second member; friction stir bonding using a rotary tool made of a large-diameter portion and a small-diameter portion being equipped with a screw, by inserting said small-diameter portion into said butted region, in a state where said large-diameter portion is inserted into each of said first convex portions of said first member and said second member; and cutting out each of said first convex portions of said first member and said second member, subsequently.
 12. A friction stir bonding method, the method comprising the steps of: butting an end portion of a first member against an end portion of a second member; inserting a convex portion projecting in said butting direction from said end portion of said first member into a concave portion provided to said end portion of said second member; and friction stir bonding while positioning the axial center of a rotary tool at approximately the center of said concave portion in the depth direction.
 13. A rotary tool for friction stir bonding, wherein: said rotary tool is comprised of a small-diameter portion being equipped with a screw, and a large-diameter portion of a different member provided to an axis end of said small-diameter portion; a surface of said large-diameter portion on said small-diameter portion side is concaved; and an end portion of said screw exists inside said concave of said large-diameter portion.
 14. A rotary tool for friction stir bonding according to claim 13, wherein: an axis end opposite to said axis end provided with said large-diameter portion is provided with a second large-diameter portion of a different member; a surface of said second large-diameter portion on said small-diameter portion side is concaved; and an end portion of said screw exists inside said concave of said large-diameter portion. 